Cryptanalysis of a High-Definition Image Encryption Based on AES Modification

Wun-She Yap, Raphael C.-W. Phan, Bok-Min Goi

Abstract: Wadi and Zainal recently proposed a high definition image encryption algorithm based on a modified AES-128 block cipher in (Wirel Pers Commun 79(2):811–829, 2014). In this paper, we show that the core component of their image encryption algorithm, a modified AES-128 cipher, is insecure against impossible differential attack. The proposed impossible differential attack on the full rounds of the modified AES-128 cipher has a time complexity of around \(2^{88.74}\) encryptions with \(2^{114.06}\) chosen plaintexts and \(2^{99}\) bytes of memory, in contrast to the expected security of \(2^{128}\). The existence of such an attack disproves the claims made by the designers that their modified AES-128 cipher improves the security of the AES cipher and that it can subsequently be used to construct a secure image encryption scheme. The root cause of this attack, some other issues with the modified AES cipher and possible solutions are described to serve as important remarks in designing a secure image encryption scheme.